Electrical Injuries Robert Primavesi MDCM CCFPEM Montreal General

Electrical Injuries Robert Primavesi, MDCM, CCFP(EM) Montreal General Hospital Mc. Gill University Health Centre

Electrical Injuries Goals • To identify the important complications of electrical injuries. • To expose the pitfalls in diagnosis. • To explore the controversies in management.

Electrical Injuries Objectives • Define the population at risk. • Determine the factors predicting the severity of injury. • Differentiate between high-voltage and lowvoltage injuries. • Recognize which patients require admission or referral. • Decide which patients need cardiac monitoring.

Top 10 Myths of Electrical Injury *

Top 10 Myths of Electrical Injury Myth #1 Electrical Injuries Are Uncommon

Electrical Injuries Epidemiology • 124 deaths in Quebec 19871992 • 5 X additional patients requiring emergency treatment • 3 -5% of all burn centre admissions • Bimodal distribution – Toddlers – Workforce

Top 10 Myths of Electrical Injury Myth #2 Voltage Is the Most Important Determinant of Injury

Electrical Injuries Factors Determining Severity OHM’S LAW: i = V / R 1. 2. 3. V = voltage i = current R = resistance

Electrical Injuries Factors Determining Severity JOULE’S LAW: Power (watts) = Energy (Joules) time =Vxi 2 =i x. R

Electrical Injuries Factors Determining Severity Mucous membranes Vascular areas • volar arm, inner thigh Wet skin • Sweat • Bathtub Other skin Sole of foot Heavily calloused palm Skin Resistivity - Ohms/cm 2 100 300 - 10 000 1 200 - 1 500 2 500 10 000 - 40 000 100 000 - 200 000 1 000 - 2 000

Top 10 Myths of Electrical Injury Myth #3 High Voltage Is More Likely to Kill Than Low Voltage

Electrical Injury Factors Determining Severity • A momentary dose of high voltage electricity is not necessarily fatal. • Low voltage is just as likely to kill as high voltage. RK Wright, JH Davis. The investigation of electrical deaths: a report of 220 fatalities. J. Forensic Sci. 1980; 25: 514 -521. Cunningham PA. The need for cardiac monitoring after electrical injury. Medical Journa of Australia. 154(11): 765 -6, June 1991.

Top 10 Myths of Electrical Injury Myth #4 The Extent of the Surface Burn Determines the Severity of Injury

Electrical Injuries Patterns of Injury • Direct contact – Direct tissue heating – Contact burns (entry and exit) – Thermal burns

Top 10 Myths of Electrical Injury Myth #5 The Pathway the Electrical Current Takes Through the Victim Predicts the Pattern of Injuries

Electrical Injuries Patterns of Injury Skin Resistivity Least Intermediate Most Nerves Blood Mucous membranes Muscle Dry skin Tendon Fat Bone

Electrical Injuries Effects of 60 Hz Current 1 m. Amp 5 m. A 6 m. A 10 m. A 20 m. A 100 m. A 6 A 20 A Threshold of perception Maximum harmless current Ground fault interrupter opens “Let-go” current Possible tetany of resp muscles VF threshold Defibrillation Household circuit breaker opens

Top 10 Myths of Electrical Injury Myth #6 • Electricity Kills by Causing Myocardial Damage • CK and/or Troponin Are Good Markers for Myocardial Damage in Electrical Injury

Electrical Injuries Patterns of Injury • James T. , Riddick L. , Embry J. Cardiac abnormalities demonstrated post-mortem in four cases of accidental electrocution and their potential significance relative to non-fatal electrical injuries of the heart. American Heart Journal. 120: 143 -57, 1990 • Robinson N. , Chamberlain D. Electrical injury to the heart may cause long-term damage to conducting tissue: a hypothesis and review of the literature. Int J Cardiol. 53: 273 -7, 1996

Top 10 Myths of Electrical Injury Myth #7 All Patients With Electrical Injury Require 24 Hours of Cardiac Monitoring

Electrical Injuries Cardiac Monitoring • Alexander L. Electrical injuries of the nervous system. J Nerv Ment Dis 1941; 94: 622 -632 • Jensen PJ, et. al. Electrical injury causing ventricular arrhythmias. Br heart J 1987; 57: 279 -283 • Norquist C. , Rosen CL. , Adler JN. , Rabban JT. , Sheridan R. The risk of delayed dysrhythmias after electrical injuries. Acad Emerg Med. 6: 393, 1999

Electrical Injuries Cardiac Monitoring Study Voltage No. of patients Initial ECG = Normal Initial ECG = Abnormal Late Arrhythmias 1000 48 40 8 0 < 1000 35 31 4 0 Moran and Munster 110 – 850 42 40 2 0 Kirschmair and Denstl 220 – 900 19 15 4 0 Fatovitch and Lee 240 20 18 2 0 Cunningham 240 70 59 11 0 Kreinke and Kienst > 220 31 29 2 0 120 and 240 120 119 1 0 > 220 73 69 4 0 Purdue and Hunt Wrobel Bailey, et. al. Arrowsmith

Electrical Injuries Cardiac Monitoring • Cardiac monitoring is not justified in ASYMPTOMATIC patients, • Or, in patients with only CUTANEOUS burns, • Who had a normal ECG after a 120 v or 240 v injury.

Top 10 Myths of Electrical Injury Myth #8 ALL Patients Who Are Asymptomatic and Who Have a Normal ECG After a 120 V or 240 V Injury Can Be Safely Discharged From the ED

Electrical Injuries Patterns of Injury • Pregnancy – Fetal monitoring is mandatory for pregnant patients • Oral commisure burns • Cataracts • Delayed neuropsychological sequelae

Top 10 Myths of Electrical Injury Myth #9 The HYDRO QUEBEC GUIDELINES Provide the Standard of Care for Electrical Injuries

Electrical Injuries Summary - The Challenges • Electrical injuries involve multiple body systems. • Entry and exit wounds fail to reflect the true extent of underlying tissue damage. • Electrical current may cause injuries distant from its apparent pathway through the victim. • Controversies exist regarding indications for admission and cardiac monitoring following low voltage injuries.

Electrical Injuries The Future • • • Surveillance electrographique des patients ayant subi une électrisation: Étude prospective multicentrique. Investigateur principal: Benoit Bailey, MD MSc FRCPC 21 sites across Quebec – including RVH, MGH, MCH Primary objectives: 1. determine the prevalence of cardiac arrhythmias in patients on initial ECG 2. determine the prevalence of late arrhythmias in patients who undergo cardiac monitoring

• Secondary objectives: – evaluate the importance of electrical injury in Quebec’s EDs – given a normal initial ECG, evaluate if late arrhythmias develop in patients with tetany, current across the heart, or with >1000 V – given a normal initial ECG, evaluate if late arrhythmias develop in patients with PMHx of cardiac disease, or decreased skin resistance – evaluate the incidence of cardiac problems in the year following electrical injury

• Secondary objectives, cont’d: – accumulate prospectively an experience with applying the Hydro Quebec protocol – determine the utility of measuring CK, CK-MB in predicting ECG abnormalities and the development of late arrhythmias – determine the utility of measuring Troponin in predicting ECG abnormalities and the development of late arrhythmias

Top 10 Myths of Electrical Injury Myth #10 “er” is an Accurate Reflection of Life in the ER

Electric Shock: What Should You Do? The victim: Felt the current pass through his/her body Yes No Was held by the source of the electric current The current passed through the heart Yes No Yes 1 second or more No Yes No Lost consciousness No Touched a voltage source of more than 1 000 volts Yes Cardiac Monitoring 24 hours

Electric Shock: What Should You Do? Page 2. Touched a voltage source of more than 1 000 volts Cardiac Monitoring 24 hours Yes No Yes Has burn marks on his/her skin Yes The current passed through the heart No Evaluate and treat burns (surgical evaluation, look for myogolbinuria, etc. ) No Was thrown from the source Yes Evaluate trauma No Is pregnant Yes Evaluate fetal activity No BENIGN SHOCK Reassure and discharge Direction Services de Sante Hydro Quebec, 1995